1. Field of the Invention
This invention relates generally to tools used to complete subterranean wells and more particularly to apparatus and methods used in gravel pack operations.
2. Description of Related Art
Hydrocarbon fluids such as oil and natural gas are obtained from a subterranean geologic formation, referred to as a reservoir, by drilling a well that penetrates the hydrocarbon-bearing formation. Once a wellbore has been drilled, the well must be completed before hydrocarbons can be produced from the well. A completion involves the design, selection, and installation of equipment and materials in or around the wellbore for conveying, pumping, or controlling the production or injection of fluids. After the well has been completed, production of oil and gas can begin.
Sand or silt flowing into the wellbore from unconsolidated formations can lead to an accumulation of fill within the wellbore, reduced production rates and damage to subsurface production equipment. Migrating sand has the possibility of packing off around the subsurface production equipment, or may enter the production tubing and become carried into the production equipment. Due to its highly abrasive nature, sand contained within production streams can result in the erosion of tubing, flowlines, valves and processing equipment. The problems caused by sand production can significantly increase operational and maintenance expenses and can lead to a total loss of the well.
One means of controlling sand production is the placement of relatively large grain sand (i.e., xe2x80x9cgravelxe2x80x9d) around the exterior of a slotted, perforated, or other type liner or screen. The gravel serves as a filter to help assure that formation fines and sand do not migrate with the produced fluids into the wellbore. In a typical gravel pack completion, a screen is placed in the wellbore and positioned within the unconsolidated formation that is to be completed for production. The screen is typically connected to a tool that includes a production packer and a cross-over, and the tool is in turn connected to a work or production tubing string. The gravel is mixed with a carrier fluid and pumped in a slurry down the tubing and through the cross-over, thereby flowing into the annulus between the screen and the wellbore. The carrier fluid in the slurry leaks off into the formation and/or through the screen. The screen is designed to prevent the gravel in the slurry from flowing through it and entering into the production tubing. As a result, the gravel is deposited in the annulus around the screen where it forms a gravel pack. It is important to size the gravel for proper containment of the formation sand, and the screen must be designed in a manner to prevent the flow of the gravel through the screen.
In order for the gravel to be tightly packed within the annulus as desired, the carrier fluid must leave the slurry in a process called dehydration. For proper dehydration, there must be paths for the fluid to exit the slurry. Dehydration of the slurry can be difficult to achieve in areas of the annulus that are not adjacent to a fluid path such as a gravel pack screen or perforations into a permeable formation. In areas where there is inadequate dehydration, the carrier fluid restricts the packing of the gravel and can lead to voids within the gravel pack. Sections of wellbore located between gravel pack screens are areas where it is difficult to achieve a gravel pack. The area of the wellbore below the lowest perforated zone is another location that can lead to voids within the gravel packed annulus. Over time the gravel that is deposited within the annulus may have a tendency to settle and fill any void areas, thereby loosening the gravel pack that is located higher up in the wellbore, and potentially creating new voids in areas adjacent to producing formations.
Once the well is placed on production, the flow of produced fluids will be concentrated through any voids that are present in the gravel pack. This can cause the flow of fines and sand from the formation with the produced fluids and can lead to the many problems discussed above.
There is a need for improved tools and methods to improve slurry dehydration and to minimize the creation of voids during a gravel pack completion of a wellbore.
The present invention provides improved apparatus and methods for use in completing a subterranean zone penetrated by a wellbore.
One aspect of the invention is an apparatus comprising a tubular member having a first segment and a second segment, each segment containing a longitudinal bore. The tubular member forms an annulus between itself and the wellbore wall. The first segment comprises the portion of the tubular member that does not contain apertures to allow fluid communication between the bore of the tubular member and the wellbore. The second segment comprises the portion of the tubular member that contains apertures to allow fluid communication between the bore of the tubular member and the wellbore. At least one screen member at least partially encloses and is coupled to a second segment of the tubular member. The screen member and the enclosed second segment of the tubular member both have openings that allow fluid communication between the longitudinal bore of the tubular member and the wellbore. The apparatus includes an alternate flowpath member having a wall, upper and lower ends, and at least one aperture in its wall. The apertures are small enough to substantially prevent the passage of particulate material from going through. The alternate flowpath member extends longitudinally along a portion of the wellbore and creates a communication path for fluid flow.
In alternate embodiments, the alternate flowpath member can be sealed on the upper end or can be sealed on both the upper and lower ends. The alternate flowpath member can also be attached to the exterior of the tubular member.
The apparatus can further comprise a plurality of screen members and second segments spaced longitudinally on the tubular member. It can likewise comprise a plurality of first segments.
In alternate embodiments of the invention, the alternate flowpath member can extend below the lowest screen member, can extend between two separate screen members, or can alternately extend between two separate first segments of the tubular member. In another embodiment the alternate flowpath member can extend at least from the uppermost screen member to below the lowest screen member. In yet another embodiment the alternate flowpath member can extend at least from the uppermost screen member to the lowest first segment of the tubular member. In still another embodiment the alternate flowpath member can comprise a slotted tubular that is sealed on both ends.
One embodiment of the present invention includes the screen members and first segments of the tubular member each forming an annulus between themselves and the wellbore wall. The alternate flowpath member can be attached to the tubular member. The alternate flowpath member can provide fluid communication between the annulus adjacent to a screen member and the annulus adjacent to another screen member. The alternate flowpath member can likewise provide fluid communication between the annulus adjacent to a screen member and the annulus adjacent to a first segment of the tubular member.
The wellbore can comprise a well casing disposed within the wellbore, the well casing comprising a perforated section and a non-perforated section. The perforated section provides fluid communication between the subterranean zone and the wellbore. The wellbore can comprise a plurality of perforated sections and non-perforated sections.
In one embodiment of the invention the alternate flowpath member extends from a perforated section of casing to a non-perforated section of casing. In another embodiment the alternate flowpath member extends at least from one perforated section of casing to another perforated section of casing. In yet another embodiment the alternate flowpath member extends at least from the lowest perforated section of casing to the lowest non-perforated section of casing. In still another embodiment the alternate flowpath member extends from above the highest perforated section of casing to the lowest non-perforated section of casing.
One embodiment of the present invention comprises a production string having at least one sand screen and an alternate flowpath member positioned outside the production string providing fluid communication substantially longitudinally with respect to the production string. The alternate flowpath member can be adapted to prevent the flow of a gravel particulate therethrough.
The alternate flowpath member can be a conduit. The alternate flowpath member can comprise apertures such as slots, small holes or a screen element that allow fluid to pass through but that are small enough to prevent the passage of a gravel particulate.
The alternate flowpath member can be positioned at least partially longitudinally offset from the sand screen. It can be positioned between adjacent sand screens, and can overlap the adjacent sand screens. The alternate flowpath member can also extend below the lowest sand screen.
The well completion can further comprise a completion zone, where the alternate flowpath extends substantially the length of the completion zone. It can also comprise where the alternate flowpath member is incorporated within the sand screens. The well completion can further comprise a protective shroud. The alternate flowpath member can be attached to the production string.
Yet another embodiment is a well completion comprising a production string having at least one sand screen and an alternate flowpath member that is attached to and positioned outside the production string comprising a conduit containing at least one aperture. The conduit apertures are sized to substantially prevent the flow of gravel particulates while providing fluid communication. The conduit is positioned to provide a fluid flowpath between one or more locations adjacent the production string without a sand screen and an area adjacent the production string having a sand screen.
Still another embodiment is an alternate flowpath member for use in a well comprising a conduit defining a passageway extending at least partially longitudinally therethrough, with at least one port through a wall of the conduit providing fluid communication into and from the conduit at two or more longitudinal locations on the conduit. The ports are adapted to prevent the flow of gravel particulates therethrough and an attachment is adapted to connect the conduit to a well production conduit. The alternate flowpath member can further comprise a screening element applied to the ports to prevent the flow of gravel particulates through the ports. The screening element can comprise a wire wrap, mesh, screen, or filter mechanism.
Another aspect of the present invention is a method for completing a well that comprises positioning a production string in a well, the production string having at least one sand screen positioned to receive fluid therethrough and providing an alternate flowpath outside the production string that provides fluid communication substantially longitudinally with respect to the production string. Fluid slurry containing gravel is injected down through the well to gravel pack an annulus formed outside the sand screen. The alternate flowpath is sized so as to substantially prevent the flow of the gravel through it.
A further embodiment is a method for creating alternate flowpaths that comprises providing a conduit having a longitudinal passageway and providing one or more flow ports between an exterior of the conduit and the passageway. A barrier is created to the flow of gravel through the passageway and the conduit is attached to a production conduit. The flow ports are sized to prevent the flow of gravel therethrough. A screen element can be included that prevents the flow of gravel through the flow ports.
Another embodiment of the present invention is a method for completing a subterranean zone penetrated by a wellbore having a wall. This method comprises the steps of providing an apparatus as described above. This apparatus is placed within the wellbore to be completed and a slurry comprising particulate material flows into the annulus area between the wellbore wall and the tubular member. In this way the particulate material is placed within the annulus between the wellbore wall and the tubular member. The alternate flowpath member provides a fluid path for the slurry dehydration.
The method can further comprise the step of attaching the apparatus to a packer and a cross-over tool, prior to positioning the apparatus within the wellbore.
The method can also comprise the step of setting the packer and flowing a slurry comprising particulate material through the packer and cross-over tool into the annulus between the wellbore wall and the tubular member. In this way the particulate material is placed within the annulus between the wellbore wall and the tubular member.